VLT Discovers First Interstellar Asteroid1:16

For the first time ever astronomers have studied an asteroid that has entered the Solar System from interstellar space. Observations from ESO’s Very Large Telescope in Chile and other observatories around the world show that this unique object was travelling through space for millions of years before its chance encounter with our star system

November 25th 2017

4 months ago

An artist's impression of the strange interstellar object ‘Oumuamua.Source:Supplied

The PanSTARRS1 telescope found a new pinprick of light crossing our skies.

It was coming from a strange direction. It was moving unusually fast.

All of which was tracked back to an interstellar origin — beyond our own Solar System.

At first it was dubbed Comet C/2017 U1.

But it proved not to be a comet.

So it was named ‘Oumuamua.

Now astronomers have figured out something about its origins, its incredibly long journey and its makeup.

The latest revelation is that it is spinning chaotically out of control.

And it is destined to do so for at least another billion years.

These diagrams show the discovery of interstellar asteroid ‘Oumuamua’ as it passes through the Solar System, its calculated track and the light sampling that has revealed its nature. Oumuamua is not bound by the Sun's gravity. Picture: ESO/K. Meech et alSource:Supplied

A PALPABLE HIT

“At some point or another it’s been in a collision,” Queen’s University astronomer Dr Wes Fraser told the BBC’s Sky At Night show after his research was published in Nature Astronomy.

In the vastness of space between the planets — yet alone the interstellar distances between stars — the odds for this are incredible. But it may be what propelled it our way in the first place.

The British based researchers have been breaking down the light patterns being bounced off the unusually dull object.

It’s previously been established as being some 200m long. At eight times longer than it is wide, it is roughly the shape of a crumpled cigar.

It was initially thought to be spinning once every seven or eight hours. But the math didn’t add up.

The variations in the dull reddish light reflected off this distant object’s surface can reveal how it’s moving. Turns out, it isn’t moving in a regular pattern.

“The tumbling actually causes stresses and strains internal to the object, and that slowly but surely squeezes and pulls on the object just like tides on the Earth to remove energy from the spin,” Dr Fraser says.

This torque has reshaped the object over the millennia. It will eventually soak up all of the energy of the spin, causing it to glide gently through space.

“It’s hard to know if it was during planet formation or after the planet formation process,” he says. “Certainly, more collisions happen while planets are growing than afterwards, so that’s a very good guess. But unfortunately we can’t get a high-resolution image of this thing to see what kind of crater is on it that might be attributed to the collision that caused it to start tumbling.”

Interstellar winds. Heat radiation. Close encounters with planets. All could have contributed to its wildly gyrating, near-eternal dance.

It didn't come from Vega.

At 26 km/s, it would have taken #A2017U1 nearly 300,000 years to travel from Vega to the Sun.

It’s also being seen as potential evidence for the theory of lithopanspermia — the transfer of microbial life between planets and stars through comets and asteroids. Such an object — crashing into our surface as a meteor — could have seeded the building blocks for life on Earth.

We haven’t sampled such an interstellar visitor, yet.

So it remains just an enticing idea.

‘Oumuamua itself isn’t going to hang around long. At its current speed, it will pass Jupiter in May and Saturn early next year.

It won’t be long until it has left our Solar System behind.

Meanwhile, astronomers are racing to find the next interstellar visitor. Or identify ones that have been snared by the Sun’s gravitational pull.

This involves backtracking orbits. Watching the skies in generally ignored directions. Analysing the spectroscopy of known objects for variations in oxygen isotope ratios that indicate they are not made of the same stuff as the rest of our Solar System.

This handout photo released by the European Southern Observatory shows an artist's impression of the first interstellar asteroid: ‘Oumuamua which seems to be a dark red highly-elongated metallic or rocky object, about 400 metres long, and is unlike anything normally found in the Solar System. Picture: AFP / European Southern ObservatorySource:AFP

WHY IS ‘OUMUAMA THE WAY IT IS?

The Search for Extra Terrestrial Life’s (SETI’s) Matija Cuk does not know. Though he does have a favourite idea.“My own favourite hypothesis is that ‘Oumuamua is a piece of a planet destroyed by tides as it was passing close to a red dwarf star in a binary system,” he writes.

“The idea is that the planet formed around the red dwarf’s companion, but its orbit was destabilised and the planet swung past the red dwarf, about to be hurled into interstellar space.”

“Red dwarf stars can be surprisingly dense, some of them are the size of Jupiter, but with a hundred times larger mass. This makes their tides very strong, and tides can disrupt bodies that come too close (like Jupiter disrupted comet Shoemaker-Levy 9 in 1994).

“If a planet can be shredded into trillions of fragments which are then ejected into interstellar space, such catastrophic events could produce more interstellar objects than regular ejections of comets and asteroids by planets.”